On the ultraviolet behaviour of quantum fields over noncommutative manifolds

By exploiting the relation between Fredholm modules and the Segal-Shale-Stinespring version of canonical quantization, and taking as starting point the first-quantized fields described by Connes' axioms for noncommutative spin geometries, a Hamiltonian framework for fermion quantum fields over noncommutative manifolds is introduced. We analyze the ultraviolet behaviour of second-quantized fields over noncommutative 3-tori, and discuss what behaviour should be expected on other noncommutative spin manifolds.Comment: 10 pages, RevTeX version, a few references adde

On the Coherent State Path Integral for Linear Systems

We present a computation of the coherent state path integral for a generic linear system using ``functional methods'' (as opposed to discrete time approaches). The Gaussian phase space path integral is formally given by a determinant built from a first-order differential operator with coherent state boundary conditions. We show how this determinant can be expressed in terms of the symplectic transformation generated by the (in general, time-dependent) quadratic Hamiltonian for the system. We briefly discuss the conditions under which the coherent state path integral for a linear system actually exists. A necessary -- but not sufficient -- condition for existence of the path integral is that the symplectic transformation generated by the Hamiltonian is (unitarily) implementable on the Fock space for the system.Comment: 15 pages, plain Te

Daily physical activity and related risk factors in COPD

Background Factors associated with reduced daily physical activity (DPA) in patients with COPD are still controversial. Physical inactivity in COPD increases risk of cardiovascular disease, frequent exacerbations, reduced health status, and increased symptoms. We hypothesised that reduced DPA in patients with COPD is independent of traditional risk factors including age and spirometry. Methods In this cross-sectional study, DPA (over 7 days) was assessed on 88 community stable patients with COPD and 40 controls free from cardiorespiratory disease. Spirometry, body composition, number of exacerbations, handgrip strength (HGS), modified Medical Research Council (mMRC), arterial stiffness, 6-min walking distance (6MWD) and BODE index were also determined. Frequent exacerbation was defined as ≥2 and non-frequent exacerbation < 2. Results Patients with COPD had reduced DPA and exercise capacity compared with controls similar in age, BMI and gender, p  0.05. The level of breathlessness was superior to lung function in predicting the level of DPA. Conclusion The level of DPA in COPD was independent of traditional risk factors. Breathlessness score is a better predictor of the DPA than lung function and handgrip strength

Does pulmonary rehabilitation address cardiovascular risk factors in patients with COPD?

Background Patients with COPD have an increased risk of cardiovascular disease. Whilst pulmonary rehabilitation has proven benefit for exercise tolerance and quality of life, any effect on cardiovascular risk has not been fully investigated. We hypothesised that pulmonary rehabilitation, through the exercise and nutritional intervention, would address these factors. Methods Thirty-two stable patients with COPD commenced rehabilitation, and were compared with 20 age and gender matched controls at baseline assessment. In all subjects, aortic pulse wave velocity (PWV) an independent non-invasive predictor of cardiovascular risk, blood pressure (BP), interleukin-6 (IL-6) and fasting glucose and lipids were determined. These measures, and the incremental shuttle walk test (ISWT) were repeated in the patients who completed pulmonary rehabilitation. Results On commencement of rehabilitation aortic PWV was increased in patients compared with controls (p < 0.05), despite mean BP, age and gender being similar. The IL-6 was also increased (p < 0.05). Twenty-two patients completed study assessments. In these subjects, rehabilitation reduced mean (SD) aortic PWV (9.8 (3.0) to 9.3 (2.7) m/s (p < 0.05)), and systolic and diastolic BP by 10 mmHg and 5 mmHg respectively (p < 0.01). Total cholesterol and ISWT also improved (p < 0.05). On linear regression analysis, the reduction in aortic PWV was attributed to reducing the BP. Conclusion Cardiovascular risk factors including blood pressure and thereby aortic stiffness were improved following a course of standard multidisciplinary pulmonary rehabilitation in patients with COPD

Quantizing the damped harmonic oscillator

We consider the Fermi quantization of the classical damped harmonic oscillator (dho). In past work on the subject, authors double the phase space of the dho in order to close the system at each moment in time. For an infinite-dimensional phase space, this method requires one to construct a representation of the CAR algebra for each time. We show that unitary dilation of the contraction semigroup governing the dynamics of the system is a logical extension of the doubling procedure, and it allows one to avoid the mathematical difficulties encountered with the previous method.Comment: 4 pages, no figure

Aortic Pulse Wave Velocity as a Measure of Cardiovascular Risk in Chronic Obstructive Pulmonary Disease: Two-Year Follow-Up Data from the ARCADE Study

Background and objectives: Cardiovascular (CV) disease is a major cause of morbidity and mortality in chronic obstructive pulmonary disease (COPD). Patients with COPD have increased arterial stiffness, which may predict future CV risk. However, the development of arterial stiffness in COPD has not yet been studied prospectively. The Assessment of Risk in Chronic Airways Disease Evaluation (ARCADE) is a longitudinal study of CV risk and other comorbidities in COPD. The aims of this analysis were to explore factors associated with aortic pulse wave velocity (aPWV) at baseline and to describe the progression of aPWV in patients with COPD and comparators over two years. Materials and methods: At baseline, 520 patients with COPD (confirmed by spirometry) and 150 comparators free from respiratory disease were assessed for body composition, blood pressure, aPWV, noninvasive measures of cardiac output, inflammatory biomarkers, and exercise capacity. This was repeated after two years, and mortality cases and causes were also recorded. Results: At baseline, aPWV was greater in COPD patients 9.8 (95% confidence interval (CI) 9.7–10) versus comparators 8.7 (8.5–9.1) m/s (p < 0.01) after adjustments for age, mean arterial pressure (MAP), and heart rate. Mean blood pressure was 98 ± 11 in COPD patients and 95 ± 10 mmHg in comparators at baseline (p = 0.004). After two years, 301 patients and 105 comparators were fully reassessed. The mean (95% CI) aPWV increased similarly in patients 0.44 (0.25–0.63) and comparators 0.46 (0.23–0.69) m/s, without a change in blood pressure. At the two-year follow-up, there were 29 (6%) deaths in COPD patients, with the majority due to respiratory causes, with an overall dropout of 43% of patients with COPD and 30% of comparators. Conclusions: This was the first large longitudinal study of CV risk in COPD patients, and we confirmed greater aPWV in COPD patients than comparators after adjustments for confounding factors. After two years, patients and comparators had a similar increase of almost 0.5 m/s aPWV

Functional Evolution of Free Quantum Fields

We consider the problem of evolving a quantum field between any two (in general, curved) Cauchy surfaces. Classically, this dynamical evolution is represented by a canonical transformation on the phase space for the field theory. We show that this canonical transformation cannot, in general, be unitarily implemented on the Fock space for free quantum fields on flat spacetimes of dimension greater than 2. We do this by considering time evolution of a free Klein-Gordon field on a flat spacetime (with toroidal Cauchy surfaces) starting from a flat initial surface and ending on a generic final surface. The associated Bogolubov transformation is computed; it does not correspond to a unitary transformation on the Fock space. This means that functional evolution of the quantum state as originally envisioned by Tomonaga, Schwinger, and Dirac is not a viable concept. Nevertheless, we demonstrate that functional evolution of the quantum state can be satisfactorily described using the formalism of algebraic quantum field theory. We discuss possible implications of our results for canonical quantum gravity.Comment: 21 pages, RevTeX, minor improvements in exposition, to appear in Classical and Quantum Gravit

Quantum Gowdy T3T^3 model: A unitary description

The quantization of the family of linearly polarized Gowdy $T^3$ spacetimes is discussed in detail, starting with a canonical analysis in which the true degrees of freedom are described by a scalar field that satisfies a Klein-Gordon type equation in a fiducial time dependent background. A time dependent canonical transformation, which amounts to a change of the basic (scalar) field of the model, brings the system to a description in terms of a Klein-Gordon equation on a background that is now static, although subject to a time dependent potential. The system is quantized by means of a natural choice of annihilation and creation operators. The quantum time evolution is considered and shown to be unitary, allowing both the Schr\"odinger and Heisenberg pictures to be consistently constructed. This has to be contrasted with previous treatments for which time evolution failed to be implementable as a unitary transformation. Possible implications for both canonical quantum gravity and quantum field theory in curved spacetime are commented

Cardiovascular and inflammatory effects of simvastatin therapy in patients with COPD: a randomized controlled trial.

BACKGROUND: There is excess cardiovascular mortality in patients with chronic obstructive pulmonary disease. Aortic stiffness, an independent predictor of cardiovascular risk, and systemic and airway inflammation are increased in patients with the disease. Statins modulate aortic stiffness and have anti-inflammatory properties. A proof-of-principle, double-blind, randomized trial determined if 6 weeks of simvastatin 20 mg once daily reduced aortic stiffness and systemic and airway inflammation in patients with chronic obstructive pulmonary disease. METHODS: Stable patients (n=70) were randomized to simvastatin (active) or placebo. Pre-treatment and post-treatment aortic stiffness, blood pressure, spirometry, and circulating and airway inflammatory mediators and lipids were measured. A predefined subgroup analysis was performed where baseline aortic pulse wave velocity (PWV) was >10 m/sec. RESULTS: Total cholesterol dropped in the active group. There was no significant change in aortic PWV between the active group and the placebo group (-0.7 m/sec, P=0.24). In those with aortic stiffness >10 m/sec (n=22), aortic PWV improved in the active group compared with the placebo group (-2.8 m/sec, P=0.03). Neither systemic nor airway inflammatory markers changed. CONCLUSION: There was a nonsignificant improvement in aortic PWV in those taking simvastatin 20 mg compared with placebo, but in those with higher baseline aortic stiffness (a higher risk group) a significant and clinically relevant reduction in PWV was shown